‘Hard on water:’ Smoke not the only long-range effect of wildfires

Smoke isn’t the only way wildfires affect people and places far from the flames.

Researchers are studying how blackened forests affect ecosystems and water quality far downstream just as hundreds of blazes in British Columbia are darkening skies as far east as Manitoba.

“Fires are particularly hard on water,” said Monica Emelko, a water treatment engineer at the University of Waterloo and a member of the Southern Rockies Watershed Project.

“If the intensity is there and enough of the watershed is burned, you can have a very significant impact on the water supply and that impact can be long-lasting.”

The project began more than 10 years ago after southern Alberta’s 2003 Lost Creek fire. Its work has proven so valuable that the team recently received about $9 million in grants to keep studying how changes in forested areas affect water.

Fires and forests have always gone together. But that relationship began to change around the turn of the century.

“Fire managers started to see wildfire behaviour that was at the extreme end or beyond anything that had been previously observed,” said Uldis Silins, a University of Alberta hydrologist and project member.

The intensity and speed of fires ramped up. Blazes that used to calm overnight kept raging. At Lost Creek, firefighters reported walls of flame 150 metres high rolling through trees at 2 a.m.

A 2016 published paper found the effects of that fire were visible in rivers and streams more than a decade later.

Runoff began earlier and was faster, increasing erosion and creating drier forests. Nutrients such as phosphorus were up to 19 times greater — good for aquatic bugs but also for algae.

“Some of these streams became choked with algae,” Silins said. “We’ve seen lasting and pretty profound impacts on water quality and aquatic ecology.”

The project has seen similar effects from other fires it’s studied. Some are detectable hundreds of kilometres downstream from the flames and have serious consequences for urban water treatment.

“You get much bigger swings in water quality,” Emelko said. “One of the biggest and most common challenges to water treatment is not water contamination, but large swings in water quality.”

Nutrients that choke streams can also create microbe growth in water pipes and distribution networks. They can react with chemicals used to purify water to form compounds that are themselves harmful.

Emelko said nutrients from fires can show up far downstream and last for years.

“They can sit there in riverbeds and reservoirs and can create a legacy of effects.”

The challenges aren’t going away.

Climate scientists have for years predicted hotter and larger wildfires. Climate change doesn’t in itself spark fires, but it loads the dice in favour of them by creating longer fire seasons and drier forests, as well as increasing the number of dead, combustible trees through climate-related insect outbreaks.

Natural Resources Canada says those effects could double the amount of boreal forest burned by the end of this century compared with recent records.

Meanwhile, those forests are the source of much of our water. Two-thirds of the water used in Alberta comes from forested landscapes.

“As we see these fires more frequently with more severity, the types of impacts to our water are likely to be seen more broadly,” said Silins.

Emelko said it’s time Canadians stopped thinking solely in terms of fire suppression and water treatment plants. As water demand increases, water security has to start where the water comes from, she said.

“Forests have not been managed primarily for water. They’ve been managed for fibre production and protection of life and property,” she said. “Disturbances like wildfires are increasingly likely and we need to adapt.

“When we started working on wildfire and water, we were told it’s a one-off issue and it’s not going to be relevant to the broader scientific community.